Internal combustion engine ignition systems



July 18, 1967, G. E. MITCHELL 3,331,362

INTERNAL COMBUSTION ENGINE IGNITION SYSTEMS Filed Aug. 24, 1964 l Inventor Gz-oeee fox/men Mme/#44 By flat/X A ttorn United States Patent 3,331,362 INTERNAL COMBUSTION ENGINE IGNITION SYSTEMS George Edward Mitchell, London, England, assignor to General Motors Corporation, Detroit, Mich a corporation of Delaware Filed Aug. 24, 1964, Ser. No. 391,622 Claims priority, application Great Britain, Sept. 7, 1963,

6 Claims. (Cl. 123-148) ABSTRACT OF THE DISCLOSURE An ignition system for an internal combustion engine where the primary of an ignition coil and a controlled rectifier are connected in series across a source of direct current. The controlled rectifier is gated on by an engine driven timing device which includes a voltage pulse generator and a transistor amplifier. The controlled rectifier is turned off when a capacitor discharges through a second controlled rectifier so as to reverse bias the controlled rectifier connected with the primary. The controlled rectifier which controls the discharge of the capacitor is triggered to a conductive condition by a winding that is inductively coupled to the ignition transformer.

This invention relates to internal combustion engine ignition systems and in particular to an ignition system employing silicon controlled rectifiers.

In an internal combustion engine ignition system according to the invention the flow of current through the primary winding of the engine ignition transformer is controlled by a silicon controlled rectifier adapted to be rendered conductive by the application to its gate electrode of pulses from a voltage pulse generator arranged to be driven in time with the engine, a capacitor is arranged so as to be charged by such current flow, and an auxiliary winding inductively coupled with the ignition transformer is connected with a second silicon con-trolled rectifier so that when a voltage pulse is induced in the auxiliary winding the second silicon controlled rectifier is rendered conductive and permits the discharge of said capacitor and thereby renders said first silicon controlled rectifier nonconductive.

With such a circuit short duration pulses are generated in the secondary winding of the ignition transformer for application by way of the ignition distributor to the engine spark plugs.

Diode rectifiers, preferably silicon diodes, are included in circuit with the transformer primary winding and said auxiliary winding to damp out undesired oscillations and prevent high voltage transients appearing in the transformer primary winding.

The voltage pulses applied to the first silicon controlled rectifier are conveniently generated by means of a pair of magnetic flux-linked members one of which is adapted to be rotated in time with the engine and is conveniently driven by the engine camshaft; and the voltage pulse induced in the other member by rotation of the first member is preferably amplified by a transistor before being applied to the gate electrode of the first silicon controlled rectifier.

The scope of the invention is defined by the appended claims; and the invention and the method by which it is to be performed are hereinafter particularly described with reference to the accompanying drawing in which the single figure is a circuit diagram of an ignition system according to the invention.

In the embodiment of the invention shown in the drawin-g opposite ends of the primary winding 1 of an ignition transformer 2 are connected to the positive side of a storage battery 3 and to the anode 4 of a first silicon controlled rectifier 5, the cathode 6 of which is connected to the negative side of the battery 3 by way of an ignition switch 7.

The gate electrode 8 of the silicon controlled rectifier 5 is connected to the collector 9 of a transistor 10 the emitter 11 of which is connected to the positive side of the battery 3 and the base 12 of which is connected to one end of a coil 14 forming part of a voltage pulse generator 15 which .is magnetically flux-linked to a rotor 16 adapted to be driven in time with the engine so as to induce voltage pulses in said coil 14. A silicon diode 13 is connected across the ends of the secondary winding 1 of the ignition transformer 2.

The collector 9 of the transistor 10 is connected by way of a load resistor 17 to a junction 18 between one side of said ignition switch 7 and the cathode 6 of the silicon controlled rectifier 5.

Connected to the cathode 6 of the silicon controlled rectifier 5 is one end of an auxiliary coil 19 which is inductively coupled to the primary winding 1 of the ignition transformer 2, the other end of the auxiliary coil 19 being connected by way of a silicon diode 20 to one end of a resistor 21, the other end of which is connected to one plate of a capacitor 22, the other plate of which is connected to the negative supply line intermediate the junction thereof with the one end of the auxiliary coil 19 and the switch 7. Said other end of the resistor 21 is also connected to the gate electrode 23 of a second silicon controlled rectifier 24 the cathode 25 of which is connected to the negative side of the battery 3 and the anode 26 of which is connected to one end of a charging resistor 27 the other end of which is connected to the positive side of the battery 3.

One side of a second capacitor 28 is connected to a junction 29 intermediate said charging resistor 27 and the anode 26 of the second silicon controlled rectifier 24 and the other side of the second capacitor 28 is connected to a junction 30 intermediate the primary winding 1 of the ignition transformer 2 and the anode 4 of the first silicon controlled rectifier 5.

The free end of the secondary 31 of the ignition transformer 2 is connected to the ignition distributor (not shown) by which the voltage pulses generated by the ignition system are applied to the engine spark plugs to fire the latter.

In the operation of the ignition system described above the rotation of the rotor 16 by the engine causes voltage pulses to be generated in time therewith in the coil 14 of the voltage pulse generator 15, such pulses being amplified by the transistor 10 and applied to the gate electrode 8 of the first silicon controlled rectifier 5 which is thereby rendered conductive and permits current to flow through the primary winding 1 of the ignition transformer 2. Such current fiow through the ignition transformer 2 induced in the auxiliary coil 19 a voltage pulse which is applied to the gate electrode 23 of the second silicon controlled rectifier 24 which is thereby rendered conductive and so provides a discharge path for the second capacitor 28 which has been previously charged by the current pulse generated in the ignition transformer 2. The discharge of the second capacitor 28 renders the first silicon controlled rectifier 5 non-conductive thereby terminating the current flow through the primary 1 of the ignition transformer 2. The effect of this series of actions is to generate short duration high voltage pulses in the secondary winding 31 of the ignition transformer 2 for application to the engine spark plugs by way of the distributor.

The diodes 13, 29 are included to prevent oscillations and damp transients in the ignition transformer primary 1 and in the auxiliary winding 19.

The system described above is self-extinguishing so that if the ignition switch 7 is inadvertently left on there is very little current drain (for example about only 1 milliampere) on the battery 3 through the transistor 10 and the load resistor 17.

I claim:

1. An ignition system for an internal combustion engine comprising, an ignition transformer having a primary winding and a secondary winding, an auxiliary control winding inductively coupled to said ignition transformer, a controlled rectifier having an anode, cathode and gate, conductor means adapted to be connected with a source of voltage, means connecting said primary winding and the anode and cathode of said controlled rectifier in series across said conductor means whereby said primary winding is energized when said controlled rectifier is gated conductive in its anode-cathode circuit, timing control means adapted to be driven by said engine providing a time varying voltage in synchronism with operation of said engine, means coupling said timing control means and the gate of said controlled rectifier whereby gate current is supplied periodically to said controlled rectifier to gate it to a conductive condition in synchronism with with operation of said engine, a capacitor, a circuit for charging said capacitor from said conductor means,a voltage responsive switching means, said voltage responsive switching means being biased to a conductive condition when a trigger voltage is applied to its terminals, a discharging circuit for said capacitor connecting the anode and cathode of said controlled rectifier and including terminals of said voltage responsive switching device whereby said capacitor applies a reverse bias to the cathodeanode circuit of said controlled rectifier when said capacitor discharges through said voltage responsive switching device, and means coupling said auxiliary control winding with said voltage responsive switching device whereby said controlled rectifier is turned off when a voltage is induced in said auxiliary control winding by current flow through said primary winding.

2. An ignition system for an internal combustion engine comprising, a source of current, an ignition transformer having a primary winding and a secondary winding, an auxiliary control winding inductively coupled to said ignition transformer, said secondary winding being adapted to be connected with a spark plug for said engine for applying a firing voltage to said spark plug, a controlled rectifier having an anode, cathode and gate, means con necting the anode-cathode circuit of said controlled rectifier in series with said primary winding and across said source of current whereby said primary winding is energized by said source of current when said controlled rectifier is gated to a conductive condition in its anode-cathode circuit, a voltage responsive switching device, a capacitor, a turn-off circuit for said controlled rectifier connecting its anode and cathode and including in a series connection said capacitor and said terminals of said voltage responsive switching device, means driven in synchronism with said engine for periodically applying turn-on pulses to the gate of said controlled rectifier, and means coupling said auxiliary control winding with terminals of said voltage responsive switching device, said auxiliary control winding having a voltage induced therein which is operative to trigger said voltage responsive switching device conductive to provide a discharge path for said capacitor when a predetermined current is developed in said primary winding of said ignition transformer.

33. An ignition system for an internal combustion engine comprising, a source of direct current, conductor means connected across said source of direct current, an ignition transformer having a primary winding, a secondary winding and an auxiliary control winding, said secondary winding being adapted to be connected with a spark plug of said internal combustion engine, a first controlled rectifier having an anode, cathode and gate, means connecting said primary winding and the anode-cathode circuit of said first controlled rectifier in series across said conductors, a second controlled rectifier having an anode, cathode and gate, a capacitor connected between the anodes of said first and second controlled rectifiers, conductor means connecting the cathodes of said first and second controlled rectifiers, timing means driven in synchronism with said engine for applying turn-on pulses to the gate of said first controlled rectifier, a circuit for charging said capacitor connected across said conductor means and including the anode-cathode circuit of said first controlled rectifier, and means connecting said auxiliary control winding and the gate and cathode electrodes of said second controlled rectifier, said control winding having a voltage induced therein after said primary winding is energized which is operative to trigger said second controlled rectifier to a conductive condition, said capacitor discharging through said second controlled rectifier to apply a turn-off pulse to said first controlled rectifier when said second controlled rectifier is triggered conductive by said auxiliary control winding.

4. The ignition system according to claim 3 where a diode is connected across said primary winding of said ignition transformer.

5. The ignition system according to claim 3 where a diode is connected between said auxiliary control winding and the gate of said second controlled rectifier.

6. An ignition system for an internal combustion engine comprising, a source of direct current, power supply conductors connected across said source of direct current, an ignition transformer having a primary winding and a secondary winding, said secondary winding being adapted to be connected with a spark plug for said engine, an auxil iary control winding inductively coupled to said ignition transformer and having a voltage induced therein when said primary winding is energized, -a first controlled rectifier having an anode, cathode and gate, means connecting the anodecathode circuit of said first controlled rectifier and said primary winding of said ignition transformer in series across said power supply conductors, a second controlled rectifier having an anode, cathode and gate, conductor means connecting the cathodes of said controlled rectifiers, a capacitor connecting the anodes of said controlled rectifiers, means connecting said capacitor between the anode of said first controlled rectifier and one of said power supply conductors whereby said capacitor is charged through said first controlled rectifier when it is gated conductive, a timing control device driven in synchronism with said engine, a transistor having input terminals coupled to said timing control device and an output terminal coupled to the gate of said first controlled rectifier, and means connecting said auxiliary control winding with the gate of said second controlled rectifier, said transistor applying turn-on pulses to the gate of said first controlled rectifier and said auxiliary control winding triggering said second controlled rectifier to a conductive condition to form a discharge path for said capacitor and provide a turn-off pulse for said first controlled rectifier when a voltage of sufficient magnitude is induced in said auxiliary control winding.

Westinghouse SCR Handbook, First Edition, Youngwood, Penn. 1963, pages 7-107, 7ll2, 7-115.

MARK NEWMAN, Primary Examiner.

LAURENCE M. GOODRIDGE, Examiner. 

1. AN IGNITION SYSTEM FOR AN INTERNAL COMBUSTION ENGINE COMPRISING, AN IGNITION TRANSFORMER HAVING A PRIMARY WINDING AND A SECONDARY WINDING, AN AUXILIARY CONTROL WINDING INDUCTIVELY COUPLED TO SAID IGNITION TRANSFORMER, A CONTROLLED RECTIFIER HAVING AN ANODE, CATHODE AND GATE, CONDUCTOR MEANS ADAPTED TO BE CONNECTED WITH A SOURCE OF VOLTAGE, MEANS CONNECTING SAID PRIMARY WINDING AND THE ANODE AND CATHODE OF SAID CONTROLLED RECTIFIER IN SERIES ACROSS SAID CONDUCTOR MEANS WHEREBY SAID PRIMARY WINDING IS ENERGIZED WHEN SAID CONTROLLED RECTIFIER IS GATED CONDUCTIVE IN ITS ANODE-CATHODE CIRCUIT, TIMING CONTROL MEANS ADAPTED TO BE DRIVEN BY SAID ENGINE PROVIDING A TIME VARYING VOLTAGE IN SYNCHRONISM WITH OPERATION OF SAID ENGINE, MEANS COUPLING SAID TIMING CONTROL MEANS AND THE GATE OF SAID CONTROLLED RECTIFIER WHEREBY GATE CURRENT IS SUPPLIED PERIODICALLY TO SAID CONTROLLED RECTIFIER TO GATE IT TO A CONDUCTIVE CONDITION IN SYNCHRONISM WITH WITH OPERATION OF SAID ENGINE, A CAPACITOR, A CIRCUIT FOR CHARGING SAID CAPACITOR FROM SAID CONDUCTOR MEANS, A VOLTAGE RESPONSIVE SWITCHING MEANS, SAID VOLTAGE RESPONSIVE SWITCHING MEANS BEING BIASED TO A CONDUCTIVE CONDITION WHEN A TRIGGER VOLTAGE IS APPLIED TO ITS TERMINALS, A DISCHARGING CIRCUIT FOR SAID CAPACITOR CONNECTING THE ANODE AND CATHODE OF SAID CONTROLLED RECTIFIER AND INCLUDING TERMINALS OF SAID VOLTAGE RESPONSIVE SWITCHING DEVICE WHEREBY SAID CAPACITOR APPLIES A REVERSE BIAS TO THE CATHODEANODE CIRCUIT OF SAID CONTROLLED RECTIFIER WHEN SAID CAPACITOR DISCHARGES THROUGH SAID VOLTAGE RESPONSIVE SWITCHING DEVICE, AND MEANS COUPLING SAID AUXILIARY CONTROL WINDING WITH SAID VOLTAGE RESPONSIVE SWITCHING DEVICE WHEREY SAID CONTROLLED RECTIFIER IS TURNED OFF WHEN A VOLTAGE IS INDUCED IN SAID AUXILIARY CONTROL WINDING BY CURRENT FLOW THROUGH SAID PRIMARY WINDING. 